How to generate the proper `url_for` a nested resource? - ruby-on-rails

Question

I am using Ruby on Rails 3.2.2 and I would like to generate a proper url_for URL for a nested resource. That is, I have:
# config/routes.rb
resources :articles do
resources :user_associations
end
# app/models/article.rb
class Article < ActiveRecord::Base
...
end
# app/models/articles/user_association.rb
class Articles::UserAssociation < ActiveRecord::Base
...
end
Note: generated named routes are like article_user_associations, article_user_association, edit_article_user_association, ...
When in my view I use:
url_for([#article, #article_association])
Then I get the following error:
NoMethodError
undefined method `article_articles_user_association_path' for #<#<Class:0x000...>
However, if I state routers this way
# config/routes.rb
resources :articles do
resources :user_associations, :as => :articles_user_associations
end
the url_for method works as expected and it generates, for instance, the URL /articles/1/user_associations/1.
Note: in this case, generated named routes are like article_articles_user_associations, article_articles_user_association, edit_article_articles_user_association, ...
However, I think it isn't "good" the way routers are builded / named in the latter / working case. So, is it possible in some way to make the url_for method to work by generating named routes like article_user_association (and not like article_articles_user_association)?
I read the Official Documentation related to the ActionDispatch::Routing::UrlFor method (in particular the "URL generation for named routes" section), but I cannot find out a solution. Maybe there is a way to "say" to Rails to use a specific named router as-like it makes when you want to change the primary key column of a table with the self.primary_key statement...
# app/models/articles/user_association.rb
class Articles::UserAssociation < ActiveRecord::Base
# self.primary_key = 'a_column_name'
self.named_router = 'user_association'
...
end

Answer 1

Your UserAssociation model is in the Articles namespace, which gets included in the named route:
# app/models/articles/user_association.rb
class Articles::UserAssociation < ActiveRecord::Base
...
end
# route => articles_user_association
# nested route => article_articles_user_association
If you remove the namespace, you will get the route helper you are looking for:
# app/models/articles/user_association.rb
class UserAssociation < ActiveRecord::Base
...
end
# route => user_association
# nested route => article_user_association
Unless you have a really good reason for keeping UserAssociation in a namespace, don't.